I hope you didn't need the risk of death to convince you to not have sex with animals. But just in case, know this: bestiality will give you penis cancer.

Researchers studied 432 men between 18 and 80 years old in rural Brazil, 118 of whom had penile cancer. Of those with the disease, 35 percent reported that they had had sex with horses, cows, pigs, chickens, and other animals. And those are just the ones who admitted it.

The scientists, who published their work in the Oct. 24 issue of the Journal of Sexual Medicine, also asked the men if this was a habit or a one-time thing. "Zoopilia" was a regular indulgence for 59 percent of them, who had sex with animals over a period of between one and five years, while 21 percent did it for more than five years. Some did it daily, others monthly.

Stop reading now if you thought or wished desperately it couldn't get any more disturbing: Men who had sex with animals also had higher rates of sexually transmitted diseases, and the researchers think that might be because they're all having group sex. More than 30-percent practiced sex with animals in groups. This is not done alone in a remote stable—it's a party!

Why does bestiality cause cancer, you ask? Stênio de Cássio Zequi, urologist in Sao Palo and lead author on the study explains it to LiveScience thusly:

"We think that the intense and long-term SWA practice could produce micro-traumas in the human penile tissue," Zequi said. "The genital mucus membranes of animals could have different characteristics from human genitalia, and the animals' secretions are probably different from human fluids. Perhaps animal tissues are less soft than ours, and non-human secretions would be toxic for us," he explained.

Dear lord. Oh and did you think this was just something that happened in Deliverance land? Think again. A 2003 study published in in the Archives of Sexual behavior found that of 114 self-defined zoophiles (Greek for animal lovers) in the United States, Australia, New Zealand and Europe, 36 percent lived in big cities and 83 percent had been to college. Nearly half worked in informatics or technology, and some of them earned high incomes.

Read lots more about the science behind "zoos" on this Scientific American blog. Though I'll understand if you choose not to.